1.Talk at QCD/CDF/Theory Jet Workshop at Fermilab, 12/16/02 (PowerPoint file, HTML file, click on animations to start them – if they don’t start automatically). Note that the HMTL version is pretty slow over the NET due to the (huge) AVI files for the animations (there is always a price for new technology). It may be better to download either the ppt file or the HTML file with the associated directory of graphics (located here) and run them locally.

2.Talk at the TeV-Scale Physics Workshop, Cambridge, 7/18/02 (PowerPoint file, HTML file, the HTML version does not handle the animations well and downloads slowly).

Here are some Flash “movies” illustrating how the kT algorithm combines calorimeter cells, i.e., the movies illustrate the order in which cells (of size 0.1 x 0.1 in a symmetric region around the 2 partons indicated by the contours) are clustered (contiguous cells of the same colors are in a single cluster; the same color can be used by more than one cluster). These are all for the case of large smearing (s = 0.25) with varying values of z, the ratio of the ET’s of the 2 partons, and d, the separation of the 2 partons. First consider the case z = 1.0 and d = 0.71 (all with R = 0.7), which illustrates the generic behavior that the first cells to be clustered are at the periphery and that the clustering tends to grow inward along radial boundaries. This inward growth continues, with only a small amount of clustering in the angular direction, until all of the cells are in a cluster. The final stage involves the clustering in the angular direction, which in the next-to-final step yields 2 clusters with essentially the kinematics of the initial 2 partons. Thus if the 2 partons have d > R, there are 2 final jets (as in the movie). If d < R, there is one final jet. For a very asymmetric situation, z < 0.2, the final stages are more irregular and the partons must be further apart to avoid completer merging. These is illustrates by movies for z = 0.1, d = 0.8 (1 final jet) and z = 0.1, d = 0.9 (2 final jets).

Here are some notes (9/20/02) on the issues of kinematics and jet definitions in PDF format with figures.

Now to look at some events generated with Pythia to correspond to jets with nominal ET's of 20, 80 and 160 Gev. In each case there is a plot of the ET weighted flow vector and a bar chart of the ET in cones of R=0.7 as a function of the eta and phi of the cone center (so you can see the jets) and also a bar chart of the ET in each tower.

Here is another way to look at these Pythias generated jet events. These plots use color to indicate the level of activity in each tower. The double graphs compare the magnitude of the flow vector (jets show up as "atolls") with the ET in the towers or the ET in cones of R = 0.7. In either case jets are clearly identified by the overlap of small magnitude flow vectors, ringed by large magnitude, with high ET towers or cones.